官方建議：如果節點超過1000不建議用Affinity，因為排程計算會消耗大量時間，當然官方也有優化方案

節點親和力

NodeAffinity：節點親和力
requiredDuringSchedulingIgnoredDuringExecution: 硬親和力，即支援必須部署在指定的節點上，也支援必須不部署在指定節點上
preferredDuringSchedulingIgnoredDuringExecution: 軟親和力，儘量部署在滿足條件的節點上，或者是儘量不用部署在被匹配的節點上

pod親和力

A應用  B應用   C應用，將a應用根據某種策略部署在一塊
    requiredDuringSchedulingIgnoredDuringExecution: 將a應用和b應用部署在一塊
    preferredDuringSchedulingIgnoredDuringExecution:  儘量將a應用和b應用部署在一塊
 

podAntiAffinity：pod反親和力

requiredDuringSchedulingIgnoredDuringExecution: 不要將a應用與之匹配的應用部署在一塊
preferredDuringSchedulingIgnoredDuringExecution: 儘量不要將a應用與之匹配的應用部署在一塊

NodeAffinity簡單使用

#匹配表示式：In：等於 Gt：大於 Lt：小於 number：不能為字串

kubectl label nodes node01 disktype=ssd
kubectl label nodes node02 disktype=ssd
kubectl label nodes node01 processor
 
=gpu

apiVersion: v1
kind: Pod
metadata:
  name: nginx-gpu
spec:
  affinity:
    nodeAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:  #必須滿足
        nodeSelectorTerms:
        - matchExpressions:         #下面這些條件是可以單獨拿出來匹配出目標
          - key: disktype        #標籤disktype
            operator
 
: In         #等於
            values:
            - ssd                # ssd
      preferredDuringSchedulingIgnoredDuringExecution: #儘量滿足
      - weight: 1
        preference:
          matchExpressions:
          - key: processor      #labels key  
            operator: In        #等於
            values:
            - gpu               # gpu
  containers:
  - name: nginx
    image: nginx
    imagePullPolicy: IfNotPresent

pod親和力和反親和力

#pod親和力
kubectl label pod bosybox meme=bus #給需要繫結的pod加個唯一標籤

---
apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
#把改例項和kube-systemnamespaces下符合的albel為k8s-calico-kube-controllers的pod部署在同一個節點（拓撲域）上
  affinity:
    podAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
      - labelSelector:
          matchExpressions:
          - key: meme
            operator: In
            values:
            - bus  
#如果寫了namespaces但是留空，他是匹配所有namespace下的指定label的pod，如果寫了那麼namespaces指定了值，就是匹配指定namespaces下單指定labels的pod
        namespaces:
          - kube-system
        topologyKey: kubernetes.io/hostname
  containers:
  - name: nginx
    image: nginx
    imagePullPolicy: IfNotPresent
    
---
……
spec:
  affinity:
    podAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
      - labelSelector:
          matchExpressions:
          - key: k8s-con
            operator: In
            values:
            - calico
        
  containers:
  
---

#反親和力
apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  affinity:
    podAntiAffinity:        #就這裡加了個Anti
      requiredDuringSchedulingIgnoredDuringExecution:
      - labelSelector:
          matchExpressions:
          - key: meme
            operator: In
            values:
            - bus  
        namespaces:
          - kube-system
        topologyKey: kubernetes.io/hostname
  containers:
  - name: nginx
    image: nginx
    imagePullPolicy: IfNotPresent

#就是儘量不部署在同一個伺服器上